This is the first report demonstrating that progressive supranuclear palsy (PSP) exists on Guam. This 75-year-old Guamanian Chamorro patient with slight dementia and rigidity with restriction of ocular up gaze was diagnosed as parkinsonism-dementia complex (PDC) of Guam clinically. However, neurofibrillary tangles (NFTs) were scarcely seen in the cerebral cortices and hippocampus, but many NFTs, composed of 15-17 nm straight tubules, were detected in the subthalamic nucleus and brain stem. A large number of tuft-shaped astrocytes were observed in the putamen and motor cortex, and numerous argyrophilic grains were seen in the CA1 and subiculum. These pathological findings are different from those of PDC and consistent with PSP. The present case indicates that PSP and PDC clinically resemble each other, and that precise neuropathological examination is indispensable for the final diagnosis of the patient with parkinsonism, dementia and disturbance of vertical external ocular movement.